Children's interaction with their environment, including written and spoken language and many perceptual-motor responses, is dependent in part on the ability to detect, remember, and utilize sequential information, predictability, and redundancy from a series of events. This proposal explores one critical aspect of this ability: children's apparently greater sensitivity to repeated events. Recent findings demonstrate that school age children, like adults, show a reaction time advantage for repeated versus nonrepeated signals. This repetition effect occurs when all possible signals are equally likely. Further, when one signal is expected because it is more probable than others, children's response times for unexpected repeated events are faster than response times for unexpected nonrepeated events. The size of these repetition effects decreases as age increases. The proposed research is intended to further describe and explain developmental changes in the magnitude of the reaction time repetition effect and to isolate factors which may contribute to these differences. Experiments address age-relted differences in: (1) the influence of the time between a response and the subsequent signal, (2) possible higher-order effects which extend backward beyond the influence of the immediately preceding trial, and (3) the relative contributions of stimulus repetition and response repetition to repetition effects. Although childen's simple reaction time (no-choice) and manual tapping rate have frequently been tested, often for diagnostic purposes, the literature on children's choice reaction time is presently very limited. Consequently, the proposed experiments will supply needed normative data on children's information processing in choice tasks in addition to exploring the repetition effect.